X-ray electro-photographing process and device

ABSTRACT

An X-ray electro-photographing exposure process and device wherein a flatly extending gas space which emits electrons under the influence of X-rays is illuminated image-like with X-rays. This gas space is limited by an insulating layer located upon a counter electrode and extending parallel to a space surface. The electrodes are supplied with direct voltage. The spacing, the amount of the applied direct voltage and the amount of the used filling gas are so selected relatively to each other that the ionic current which emerges in image-like distribution due to the image-like illumination, is so accelerated in field direction that an impulse ionization takes place and thereafter a multiplying of the secondary ions is produced. An extinguishing gas is used in the intermediate space in a known manner to avoid a standing discharge. The invention is particularly characterized in that the electrodes are divided into small strips extending parallel to each other and that the gas space is subjected to increased pressure.

United States Patent 1 1 Reiss X-RAY ELECTRO-PHOTOGRAPHING PROCESS AND DEVICE [75] lnventor: Karl-Hans Reiss, Erlangen, Germany [73] Assignee: Siemens Aktiengesellschaft,

Erlangen, Germany 22 Filed: May 16, 1973 21 Appl. No.: 360,824

[30] Foreign Application Priority Data May 29, 1972 Germany 2226130 .52 us. 01. 250/315, 250/472 [51] Int. Cl G03g 15/00 [58] Field of Search.'. 250/315 [56] References Cited FOREIGN PATENTS OR APPLICATIONS 1,497,093 8/1970 Germany 250/315 Primary Examiner-James W. Lawrence Assistant Examiner C. E. Church Attorney, Agent, or Firm-Richards and Geier [451 Apr. 9, 1974 5 7] ABSTRACT An X-ray electro-photographing exposure process and device wherein a flatly extending gas space which emits electrons under the influence of X-rays is illuminated image-like with X-rays. This gas space is limited by an insulating layer located upon a counter electrode and extending parallel to a space surface. The electrodes are supplied with direct voltage. The spacing, the amount of the applied direct voltage and the amount of the used filling gas are so selected relatively to each other that the ionic current which emerges in image-like distribution due to the image-like illumination, is so accelerated in field direction that an impulse ionization takes place and thereafter a multiplying of the secondary ions is produced. An extinguishing gas is used in the intermediate space in a known manner to avoid a standing discharge. The invention is particularly characterized in that the electrodes are divided into small strips extending parallel to each other and that the gas space is subjected to increased pressure.

7 Claims, 5 Drawing Figures X-RAY ELECTRO-PHOTQGRAPHING PROCESS AND DEVICE This invention relates to an X-ray photographing exposure process and means wherein a flat shaped electrode which emits electrons under the influence of X- rays, is illuminated with X-rays forming an image. An insulated inscribing material is mounted upon a counter electrode and extends parallel and at a distance from the first-mentioned electrode. The intermediate space is filled with ionizable gas. A direct voltage is applied to the electrodes. The spacing, the amount of the applied direct voltage and the used filling gas are so selected in relation to each other that the electronic current emerging in image-like distribution due to the image illumination, is so accelerated in field direction that an impulse ionization takes place and that thereafter a multiplying of the secondary ions is produced. An extinguishing gas is used in the intermediate space in a known manner to avoid a standing discharge.

Devices which carry out these processes produce, as is known, visible pictures which appear without the use of expensive photographic layers and without having to carry out a photographic process requiring the use of many developing baths. By comparison, the insulating layer is a cheap inscribing material which can be used several times. (As described, for example, in the German publication Zentralblatt fur die gesamte Radiologie 49 (1956) pages 117-118).

The above process was substantially improved by directing the electronic current in the above-described manner in the field direction and so accelerating it that an impact ionization takes place which produces a further secondary multiplying (described for example, in German Pat. No. 1,497,093). Devices of this type produce X-ray pictures of objects up to a size of about 200 mm diameter. However, great difficulties are involved in case of larger sizes. This is caused by the fact that the plates of the device must lie precisely parallel to each other so as to provide everywhere the same field strength and thus the same charge multiplication. The high strengthening which can be produced with the described device, makes possible the creation of charged pictures with a dose which can be practically as small as desired. However, the exposure is limited by the number of effectively absorbed X-ray quanta. This last number due to the bad efficiency when changing X-ray quanta into electrons at the cathode, is very low (about 1 percent).

An object of the present invention is to eliminate these drawbacks of existing devices by dividing the electrodes into narrow electrically interconnected strips which extendparallel to each other and by using gas under higher pressure.

Other objects of the present invention will become apparent in the course of the following specification.

The present invention-makes use of the fact that the adjustment precision of the arrangement of the electrodes when non-homogenous electrical fields are used is substantially smaller. Thus the following formula represents the concentric arrangement with the electron radii r, and r for the field strength:

Thus a change in the radius r, proceeds, for example, only logarithmically. The multi-wire proportional chamber is a utilization of this consideration. The surge strengthening used by the present invention takes place in this chamber only in the direct closeness to the anode wires since only there exists the required high field strength. Thus in accordance with the present invention the anode is divided into a plurality of elements with high curvature. Furthermore, the image carrier is so thin that the electrical field in the gas chamber on the one hand is sufficiently homogenous and on the other hand the image carrier can carry the charges without disruption.

As insulating material can be used polycarbonates, possibly in the shape of foils which are 2 to 10 um thick. In accordance with a realized embodiment of the present invention a parallel screen of thin lines is used, wherein 10 lines per millimeter are applied. As conducting material aluminum ,is steamed on behind a screen of wires in the form of lines. As an insulation coating a layer of steamed on polycarbonate is applied which is 5 ,urn thick.

The parallel lines of the electrode can be also applied by etching with photo-resisting lacquers and possibly high value organic steamed on layers with polymerization by ultra violet rays or electrons. Electrode surfaces provided with the lacquer or polymerization layer and having desired locationsfrom which these layers are removed, are thereupon steamed with conducting material and for final production are freed from polymerization or photoresisting lacquer, so that electrode lines remain only on the desired locations.

It is known from the technology of the proportional counting tube that gases of sufficiently high ordinal number such as for example, xenon, when when subjected to sufficiently high pressure have a considerable absorption for X-rays. However, xenon is too expensive for a camera useable in general X-ray technology. However, methane iodide (CH J) has a practically equally high absorption. To bring it to a pressure of 760 torr it is necessary to heat it to' 42.3" C. Pressure increased to 1,500 torr is produced at 58 C. Methane io dide will also produce adequate pressure distributions at temperatures which are easily produced in practice.

Due to the guiding of .the produced charge carriers in the field it is possible to use larger stretches in gas than in the dissolved point distances. Thus already in known devices wherein two plates form the electrodes of the exposure device at about atmospheric pressure and a distance of the plates of 1 mm, solutions of five lines per millimeter can be produced. Therefore it is possible to use gas stretches of 3 mm in CH at 1,500 torr, wherein about 6 percent of rays of 50 keV are absorbed. Under these conditions it is possible to produce useable X-ray pictures with rays of l milliroentgen. Thus a comparison can be made with X-ray exposures with magnifying foils, while xeroradiographs would require a multiple dose.

Other gases useable'in the ionization chamber are, for example, ethane iodide and butane iodide. They also attain sufficiently high pressure at low temperatures, namely about C. When the exposure chamber is thermically insulated to some extent pure iodine can be also used and then to attain pressure of over 1,000 torr it is necessary to use a heating of about C. Care must be taken, however, that in case of a medical use the body of the patient being examined should be kept away from the hot parts.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawing showing by way of example only, a preferred embodiment of the inventive idea.

In the drawing:

FIG. 1 is partly a section and partly a side view of an exposure chamber constructed in accordance with the present invention.

FIG. 2 is a section through a portion of the chamber, showing the applied image carrier, namely, the synthetic film.

FIG. 2a illustrates the arrangement of the electrode strips.

FIG. 3 is a diagram showing the pressuretemperature relationship of different gases suitable for filling the exposure devices of the present invention.

FIG. 4 is a diagram showing the X-ray absorption of methane iodide depending upon the quality of the rays.

FIG. 1 shows a frame 1 which is rectangular corresponding to the desired exposure shape and which carries gas tightly an inlet plate 2 having a thickness of 1 mm and consisting of hard magnesium. Upon the surface directed to the interior of the chamber the plate carries, possibly upon an intermediate insulating layer, the electrode strips 3, which have athickness of 1.5 pm, a width of 25 um and are located next to each other at a distance of 75 m. They consist of aluminum and at both ends they are electrically connected with each other and with a current source 4 by conduits 3 and 3". The source 4 provides a maximum of SkV. The frame also includes at two opposed sides a gas inlet 5 and a gas outlet 6 by which the chamber can be filled with methane iodide which is under pressure of 1,500 torr. The frame 1 is removably connected by a seal 7 with the bottom portion 8 of the chamber. The bottom portion consists of steel and acts at the same time as the counter electrode which is connected with the negative pole of the current source 4.

To make an exposure a voltage of 3.8kV is applied to the electrode lines 3 and the counter electrode 8. The ions are produced in the gas space 9 (FIG. 2) which due to the location of the field receive acceleration to the strips 3. They are collected upon the foil 10 shown in FIG. 2, which has a thickness of Sam and consists of polycarbonate. After the frame 1 has been raised from the bottom part 8, they are removed and conducted to a powder development in a manner known in xerography.

After the powder image has been transmitted in a known manner upon an image carrier, namely paper or foil, the plate 2 is cleaned and is then ready for a new exposure.

It is advantageous for the making of an exposure to provide a uniform weak charge upon the foil 10, for example, a positive charge, since thus greater charging contrasts are attained.

Curves shown in FIG. 3 indicate that methane iodide CH used in the gas space 9, as well as other substances, namely uranhexafluoride UP ethane iodide C H -J and butane iodide C H J as well as iodine J reach in the stretch up to C the useable pressure of over 1,000 torr. For methane iodide 1,500 torr are reached at 58 C.

FIG. 4 shows the percentage of absorption per cm and ata and indicates that the absorption edge of the iodized hydrocarbon methane iodide lies between 30 and 40 keV, namely, in diagnostically important X-ray range.

I claim:

1. In an X-ray electrophotographing exposure process using a gas space having an electrode carrying surface and a spaced opposed surface constituting a counter electrode, the steps of projecting into said space X-rays forming an image, applying direct voltage to the electrodes and supplying a gas to said space, the distance between said surfaces, the amount of said voltage and the amount of said gas being so related to each other that the ionic current which emerges in imagelike distribution due to the image-like illumination, is so accelerated in field direction that an impulse ionization takes place and thereafter a multiplying of the secondary ions is produced, and finally introducing an extinguishing gas into the space to avoid a standing discharge, wherein one of said electrodes is divided into a plurality of thin strips extending parallel to each other and wherein the first-mentioned gas is under high pressure.

2. A process according to claim 1, wherein the firstmentioned gas is heavy atomic.

3. A process according to claim 2, wherein the firstmentioned gas is an iodine containing organic compound.

4. An X-ray electrophotographing exposure device, comprising means constituting a gas space and having opposed longitudinally extending top and bottom plates, said top plate being an inlet for X-rays and comprising an insulating foil and electrodes carried upon the surface of said foil and facing the bottom plate, said'electrodes consisting of narrow strips extending parallel to each other, said bottom plate being a counter electrode, said means having means introducing gas under high pressure into the gas space.

5. A device according to claim 4, wherein the distance between the electrodes is 0.3 to 5 mm., and wherein the insulating foil has a thickness of 0.3 to 10am.

6. A deivce according to claim 5, wherein the distance between the electrodes is 3 mm.

7. A device according to claim 5, wherein the insulating foil has a thickness of 5am. 

2. A process according to claim 1, wherein the firstmentioned gas is heavy atomic.
 3. A process according to claim 2, wherein the firstmentioned gas is an iodine containing organic compound.
 4. An X-ray electrophotographing exposure device, comprising means constituting a gas space and having opposed longitudinally extending top and bottom plates, said top plate being an inlet for X-rays and comprising an insulating foil and electrodes carried upon the surface of said foil and facing the bottom plate, said electrodes consisting of narrow strips extending parallel to each other, said bottom plate being a counter electrode, said means having means introducing gas under high pressure into the gas space.
 5. A device according to claim 4, wherein the distance between the electrodes is 0.3 to 5 mm., and wherein the insulating foil has a thickness of 0.3 to 10 Mu m.
 6. A deivce according to claim 5, wherein the distance between the electrodes is 3 mm.
 7. A device according to claim 5, wherein the insulating foil has a thickness of 5 Mu m. 